A surface scale being formed on the stainless steel in hot working and/or heat treatment process is removed in a descaling line by immersing, for example, into a sulfuric acid or a hydrochloric acid solution, or in a supplemental acid solution after being treated in a salt bath. And then, a surface finishing process has been further carried out in order to give a corrosion resistance or brightness to the surface.
And the process of immersing into the nitric-hydrofluoric acid solution or into the nitric acid solution has been carried out conventionally for the surface finishing process. However, for such grade of stainless steel as, for example, high carbon containing martensite stainless steel or sulfur containing free cutting martensitic stainless steel, those conventional processes have been showing problems of giving a yellowish, greyish or spotted colour to the surface and to give an inferior brightness to the surface of the stainless steel.
The purpose of this invention is to provide a novel surface finishing process where yellowish, greyish or spotted colour will not arise on the surface of the stainless steel. Namely, the purpose of this invention is to provide a new surface finishing process being carried out after the descaling process, wherein a beautiful, bright and milky white coloured surface can be obtained even for such stainless steel as high carbon containing about 17 chromium steel (JIS SUS440C etc) and high sulphur containing 13 chromium steel (JIS SUS416, SUS420F etc), instead of the conventional surface finishing process where rough, yellowish and greyish coloured surface has been resulted.